Profile of sex steroids and its relation to cortisol levels in females of Astyanax bimaculatus and Astyanax fasciatus(Characiformes: Characidae) during induced spawning in captivity

Abstract

The reproductive cycle in fish is neuromodulado by external factors such as photoperiod, temperature, rainfall and rainfall. Once the animal has reached the minimum biological conditions to start it, the external stimuli received by receptor organs, converted into electrochemical signals, they stimulate the synthesis and release of gonadotropin-releasing hormone (GnRH), which via the bloodstream, stimulates the pituitary gonadotrophic cells to initiate the synthesis and release of FSH (follicle stimulating hormone) initiating the process leading to conversion of cholesterol to testosterone. Testosterone is transported to the granular layer, and flavored to 17²-estradiol (E2), which acts on the liver, stimulating the synthesis of vitellogenin, a glicolipofosfoproteína, which via the bloodstream, is "built" by the oocyte via micropinocitose, thus promoting growth of the oocyte and the incorporation of the calf. In response to sharp production of E2, there is a negative feedback to FSH and together with the action of GnRH stimulates the secretion of LH (luteinizing hormone), which once connected to its receptors in the granular layer, will act on the ovarian follicles, initiating the process of final maturation and thus ovulation. This whole cycle can be regarded as a very sensitive stage to environmental stimuli and may even change the stress levels of individuals who have undergone variants, such as reproductive migration in some species, temperature or rainfall, can reduce circulating levels of sex steroid hormones. Stimuli capable of generating high levels of stress can also produce different responses in different stages of maturation, affecting the quality of gametes and may influence the reproduction of their offspring. Additionally, for many species of Neotropical fishes, the reproductive process is blocked somehow, when these animals are transferred to the captive, growing operations, and probably the stress generated by the maintenance of these animals in a confined environment, can be a indicator of this block. In this sense, interference hormone are required to provide the final maturation and ovulation in these Neotropical species. Thus, several recent studies have attempted to measure the influence of stress in the final stages of the reproductive event in Neotropical species with blocking reproduction in captivity, as is the case of this project therefore seeks to understand the correlation between stress and reproductive capacity two teleost species are phylogenetically close, both in deadlock captive breeding: Astyanax bimaculatus and Astyanax fasciatus. (AU)